Abstract: A heat exchanger of a structurally self-supporting plate type and provided with an internal flow passage constrained between a first and a second plate and extending between an inlet and an outlet; The flow passage is subdivided in multiple generally parallelly directed longitudinally extending channels with the longitudinally extending channels having continuous joints formed by the two plates; The longitudinally extending channels have an arch-shaped cross-section and the arch-shape of the plates of the channels is in the same face direction orthogonal to the plates; The parallel running longitudinally extending channels include several laterally directed arches relative to their main axis in their longitudinal extension.